Structural and regulatory studies will be continued with the trp operons of various bacteria. The mechanisms of transcription regulation of the trpS and tnaA operons will continue. Fusions and trpR and lacZ will be used to determine how trpR is regulated and how this regulation is accommodated in the overall regulation of tryptophan biosynthesis. Selected genes of Neurospora crassa will be cloned and their structural, regulatory and evolutionary features explored.